The present invention, in some embodiments thereof, relates to providing audio applications and ultrasonic applications through the same microphones and, more particularly, but not exclusively, to carrying out simultaneous noise cancellation and stylus localization on the sonic and ultrasonic signals respectively.
One example of use of noise cancellation is in teleconference equipment. When a voice of a speaker is localized by a microphone, noise arising from directions other than the speaker is attenuated, producing better quality transmission of the speaker's voice. Other examples of noise cancellation use special microphones which subtract peripheral noise from a voice entering the front of the microphone. In voice applications a popular microphone type is a condenser microphone.
Stylus localization using sound waves requires a more accurate localization than that achieved by audio wavelengths, in addition to the fact that an ultrasound stylus does not annoy users with audible noise. Better localization can be achieved by using shorter audio wavelengths, that is, ultrasonic wavelengths, but it is noted that condenser microphones do not have good sensitivity to ultrasonic frequencies. On the other hand, ultrasonic sensors usually have poor sensitivity in the sonic band.
PCT Patent Application No. IB 2008/050946 of Altman et al, describes an ultrasonic acoustic positioning system using a MEMS (Micro Electro-Mechanical Systems) microphone.
Existing products and technologies which process sound typically have separate sensors for ultrasound and for voice applications.
Additional background art includes:
PCT Published Patent Application No. WO2004010275, which describes position information input into an information processing system in, e.g. a mobile communication terminal. The system comprises a plurality of microphones located at known microphone positions and connected to processing circuitry capable of interpreting sound signals from the microphones. A sound signal is received from each microphone, the signals originating from an acoustic wave emanating from an acoustic sound source located at a first position. A respective difference in distance between the sound source at said first position and respective microphone is then calculated, followed by a calculation, using a geometric model, of an estimate of said first position, said estimate being position information intended for use in the information processing system.
UK Patent GB2388077 describes a stylus which contains an ultrasound transmitter for transmitting position signals and a second transmitter for transmitting a timing signal which may be infrared. A detector assembly has position signal receivers (condenser microphones) and a timing signal receiver on a base appliance which also contains hardware and firmware to enable the stylus or an eraser to be tracked on writing surfaces, such as whiteboards, blackboards, flip charts or tablet PCs. It also has a detachable personality module which contains user-related interactions and/or displays, such as push buttons and LEDs and/or LCDs. The personality module contains logic for communications and stand-alone functions. The detector assembly also has a detachable nameplate. The detector may be used without an external processor to record writing in local storage, for subsequent transfer and display. Alternatively, it may be used with an external display unit.
U.S. Pat. No. 6,577,299 describes a wireless pen apparatus for producing signals representative of writing by a user, including: a wireless pen; a removable cap on the pen; and, when the cap is removed from the pen and placed at a reference position, communicating wave energy between at least one location on the pen and at least one location on the cap for determining the position of the at least one location on the pen with respect to the reference position of the cap, and for producing signals that depend on the determined position of the at least one location on the pen.
US Published Patent Application No. 2003/071798 describes a system for generating digital ink from triangulation data of a stylus comprises an electromagnetic radiation source capable to emit electromagnetic pulses; a first and a second ultrasound detector separated from each other by a known distance; a timer coupled to the radiation source, the first detector, and the second detector, and capable to measure a first elapsed time between emission of an electromagnetic pulse from the radiation source and detection of an ultrasound wave at the first detector, and further capable to measure a second elapsed time between emission of the electromagnetic pulse from the radiation source and detection of an ultrasound wave at the second detector; and a triangulation engine coupled to the timer and the radiation source, the engine capable to instruct the source to emit a plurality of radiation pulses, to triangulate the position of an ultrasound transponder over time based on the first elapsed time, the second elapsed time and the known distance between detectors, and to generate characters based on the triangulation data.
PCT Published Patent Application WO 03/088136 of Altman et al describes a position detection system for use in association with computing applications, the system comprising: a positional element for attaining a position and comprising a first emitter for emitting a substantially continuous ultrasonic waveform decodable to fix said position, and a detector arrangement for detecting said waveform in a manner permitting fixing of said position and outputting said waveform for computation, in a manner retentive of said position fixing ability.
US Published Patent Application No. 2006/077188 discloses a device and method for inputting characters or drawings on a mobile terminal using a virtual screen. To input characters or drawings through a virtual screen, the mobile terminal includes an electronic pen, a virtual screen generator, a position detector for detecting the electronic pen position, and a character recognition algorithm for recognizing a trail as a character. When a signal is input from the electronic pen, the mobile terminal detects the originating position of the signal and its trail. The mobile terminal recognizes the detected trail as a character and generates a virtual screen with the recognized character.